MEXICO CITY — A Mexican judge Friday acquitted a reputed drug cartel "queen" of organized crime and other charges, the latest setback for a judicial system that has failed to convict the majority of suspects captured for drug crimes.

Judge Fernando Cordova del Valle ruled that prosecutors failed to bring enough evidence against Sandra Avila Beltran, described by U.S. and Mexican officials as a major decision-maker for the Sinaloa gang, Mexico's most powerful cartel. The "Queen of the Pacific" had been charged with organized crime, conspiracy to traffic drugs and money laundering.

Avila Beltran, who was arrested in September 2007 by more than 30 federal agents as she sipped coffee in a Mexico City diner, has faced a U.S. extradition request since November 2007.

The request relates to the 2001 seizure of more than 9 tons of U.S.-bound cocaine aboard a fishing vessel in the port of Manzanillo, along Mexico's west coast.

It was unclear if Avila, who remains in a Mexico City prison, still faces lesser charges or if the ruling Friday would affect the extradition process. The Attorney General's Office said it could not immediately comment.

Her boyfriend, Colombian Juan Diego Espinoza Ramirez, was also absolved in the same ruling. However, Espinoza was extradited to Florida in December 2008 on charges related to the cocaine shipment. Mexican law allows suspects to be extradited to the U.S. even while they are facing trial in the Mexico.

At the time of her arrest, prosecutors said Avila spent more than a decade working her way to the top of Mexico's drug trade, seducing several notorious kingpins and uniting Colombian and Mexican gangs.

Avila comes from a family of powerful drug lords: She is the niece of Miguel Angel Felix Gallardo, "the godfather" of Mexican drug smuggling, who is serving a 40-year sentence in Mexico for drug smuggling and the murder of DEA agent Enrique Camarena in Mexico's western Jalisco state. Another uncle, Juan Jose Quintero Payan, was extradited to the U.S. on drug-trafficking charges.

Prosecutors had said it was Avila's romance with Espinoza that brought together the Sinaloa gang and Colombia's Norte del Valle cartel.

But Avila had largely gone unnoticed until police found the cocaine shipment in Manzanillo in 2001 and tracked it to Espinoza Ramirez. A few months later, her teenage son was kidnapped in the northern city of Guadalajara and she contacted authorities for help. The size of the ransom demanded, which police said was $5 million, raised suspicion.

Officers began tracking Avila closely in Mexico City, where she dined a pricey Thai restaurant and had her hair colored jet black and hands manicured in ritzy beauty shops frequented by TV stars.

The story of her arrest enthralled Mexicans, inspiring a "narcocorrido" folk ballad by Los Tucanes de Tijuana that pays homage to her as "a top lady who is a key part of the business."

The brief statement on her acquittal offered few details on the case against her, saying only that prosecutors failed to prove the "time, place, methods" of her alleged crimes.

Avila has proclaimed her innocence from prison, saying she made her money selling clothes and renting houses.

Most trials in Mexico are conducted in writing, offering little insight into the process. That is something the country is changing through a sweeping U.S.-backed reform that will institute oral trials and transform Mexico's inquisitorial judicial system into an accusatorial one.

The Mexican government frequently touts arrests of drug gang suspects, often parading the most-wanted ones before the cameras. But records obtained by The Associated Press show that three-quarters of those arrested for drug crimes during the administration of President Felipe Calderon have been let go.

The U.S. lamented Mexico's dysfunctional judicial system in a Jan. 29 diplomatic cable released Thursday by the Wikileaks website, noting: "Prosecution rates for organized crime-related offenses are dismal; 2 percent of those detained are brought to trial."

Among those are 11 mayors who were arrested in a dramatic 2009 sweep against more than 30 officials accused of protecting the La Familia cartel in western Michoacan state. One by one, the officials have been released for lack of evidence and only one, a mayor, remains in prison.

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